MSU Study: Diet Could Affect Women’s Blood Pressure

Two Michigan State University (MSU) researchers have teamed up to take a closer look at how diet may affect the likelihood of developing high blood pressure — also known as hypertension — later in life.

Claudia Holzman, professor and chair of the MSU Department of Epidemiology and Biostatistics, and Jenifer Fenton, associate professor in the MSU Department of Food Science and Human Nutrition, are collaborating on the project with Janet Catov, associate professor from the University of Pittsburgh. The trio is using data collected from a cohort of women followed over time, first during pregnancy and then seven to 15 years later, in a series of studies funded by the National Institutes of Health.

The initial Pregnancy Outcomes and Community Health (POUCH) study enrolled more than 3,000 pregnant women from 52 clinics in five Michigan communities: Flint, Grand Rapids, Lansing, Kalamazoo and Saginaw. It spanned from 1998 to 2004 and assessed maternal health, including blood pressure, in relationship to adverse outcomes such as preterm delivery and low birthweight. In the follow-up study (POUCHmoms 2011-2014), investigators invited back a subset of the original cohort to reassess their cardiovascular health and, for the first time, their eating habits. The women in the study completed an extensive survey about their food consumption called the Block food frequency questionnaire.

“The diet questionnaire is very detailed and asks about average servings of all types of food over the previous year,” Holzman said. “It takes about 40 minutes to complete and provides summary feedback so that women can see what their diets look like. Once we amassed all the diet data, I looked for research collaborators with expertise in nutrition and health.”

That’s when Fenton, who has a master’s degree in public health in epidemiology and a Ph.D. in nutrition, entered the picture. She and Holzman met while discussing the development of a public health nutrition concentration in the nutritional sciences curriculum revision and discovered they had common research interests. Holzman turned to Fenton because of her background in nutrition and epidemiology and asked about ideas on how to further use the diet data from the POUCHmoms follow-up study. Fenton suggested that they compare the healthy eating index and the DASH (Dietary Approaches to Stopping Hypertension) diet patterns of eating to examine associations between diet and both prehypertension and hypertension in the POUCHmoms participants.

Though many studies have looked at hypertensive individuals, few have focused on those with moderately elevated blood pressure. The diet plan called DASH is often used for people diagnosed with hypertension. It is supported by the National Heart, Lung and Blood Institute and has been shown to reduce blood pressure in clinical settings, with results similar to those from medication.

“DASH has a lot of studies behind it,” Fenton said. “This is in randomized clinical controlled studies where they put those people on this diet and they show a similar reduction in blood pressure as effective as first-line therapy in stage 1 hypertension. Diet along with lifestyle changes are the first line of defense now for folks who have blood pressure of 129 and over.”

The researchers used the POUCHmoms study data to examine diet quality measured by both the healthy eating index and the DASH diet index. They found that women with the lowest quality diets had higher blood pressure, on average, at follow-up. Also, among women who had moderately elevated blood pressure during the POUCH study pregnancy, those with a low-quality diet at follow-up (seven to 15 years after pregnancy) were more likely to be prehypertensive or hypertensive.

“Previously, moderately elevated blood pressure in pregnancy had been ignored,” Holzman said. “We are finding it may identify a group of woman at increased risk of hypertension later in life, and poor-quality diet could be part of this story.”

“We think this study is unique,” she said. “We’re looking at middle-aged women – more often these studies are done with men. In addition, the participants are all from Michigan and have been followed over a long period of time, beginning in pregnancy. We are among a growing group of investigators who view pregnancy as an important window because it offers clues to a woman’s risk of future health problems such as hypertension. Our data suggest a high-quality diet might modify that risk later in life.”

Fenton said the researchers plan to look more closely at the diet data to determine if there is some component in the high-quality diet that may be linked to lower blood pressure.

“There are foods that are rich in bioactive components that might be responsible for the results we’re seeing,” she said. Holzman added it’s been known for a while that women diagnosed with hypertension in pregnancy are more likely to develop hypertension later. But when you exclude this group, the women in the bottom quartile of diet quality were the only other group at increased risk of developing hypertension.

“So if you think of exercise, you don’t have to be a high-performance athlete to get some benefit,” she said. “It may be a similar principle with food. You benefit from eating a moderately well-balanced diet rich in fruits, vegetables and fiber like the DASH and healthy eating index.”

Holzman noted that the study does take into account other relevant factors such as race/ethnicity, maternal age, education level, socioeconomic status and smoking. The researchers are eager to submit their findings for peer review and publication.

Statistics show that one in every three American adults — 70 million people — has high blood pressure. And costs of treatment, including healthcare services, medications and missed days of work, are estimated at some $46 billion each year.